Multizone control of lamps in a conical lamphead using pyrometers

ABSTRACT

A method and apparatus for processing a semiconductor substrate is described. The apparatus is a process chamber having an optically transparent upper dome and lower dome. Vacuum is maintained in the process chamber during processing. The upper dome is thermally controlled by flowing a thermal control fluid along the upper dome outside the processing region. Thermal lamps are positioned proximate the lower dome, and thermal sensors are disposed among the lamps. The lamps are powered in zones, and a controller adjusts power to the lamp zones based on data received from the thermal sensors.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 14/292,300 filed May 30, 2014 which is also acontinuation of co-pending U.S. patent application Ser. No. 13/796,169filed Mar. 12, 2013, now granted as U.S. Pat. No. 8,772,055, whichclaims benefit of U.S. Provisional Patent Application Ser. No.61/753,002, filed Jan. 16, 2013 and U.S. Provisional Patent ApplicationSer. No. 61/753,305, filed Jan. 16, 2013. Each of the aforementionedpatent applications is incorporated herein by reference.

FIELD

Methods and apparatus for semiconductor processing are disclosed herein.More specifically, embodiments disclosed herein relate to methods andapparatus for zoned temperature control in an epitaxy process.

BACKGROUND

Epitaxy is a process that is used extensively in semiconductorprocessing to form very thin material layers on semiconductorsubstrates. These layers frequently define some of the smallest featuresof a semiconductor device, and they may have a high quality crystalstructure if the electrical properties of crystalline materials aredesired. A deposition precursor is normally provided to a processingchamber in which a substrate is disposed, the substrate is heated to atemperature that favors growth of a material layer having desiredproperties.

It is usually desired that the film have very uniform thickness,composition, and structure. Because of variations in local substratetemperature, gas flows, and precursor concentrations, it is quitechallenging to form films having uniform and repeatable properties. Theprocessing chamber is normally a vessel capable of maintaining highvacuum, typically below 10 Torr, and heat is normally provided by heatlamps positioned outside the vessel to avoid introducing contaminants.Control of substrate temperature, and therefore of local layer formationconditions, is complicated by thermal absorptions and emissions ofchamber components and exposure of sensors and chamber surfaces to filmforming conditions inside the processing chamber. There remains a needfor a epitaxy chamber with improved temperature control, and methods ofoperating such a chamber to improve uniformity and repeatability.

SUMMARY

Embodiments described herein provide a substrate processing apparatusthat includes a vacuum chamber comprising a transparent dome and atransparent floor, a substrate support disposed inside the vacuumchamber, a plurality of thermal lamps arranged in a lamphead andpositioned proximate the transparent floor of the vacuum chamber, aplurality of thermal sensors disposed within the lamphead and orientedto receive thermal radiation from an area proximate the substratesupport, a plurality of power supplies coupled to the thermal lamps inrelation to the position of the thermal sensors, and a controller thatadjusts the power supplies based on input from the thermal sensors. Thetransparent dome and transparent floor may be quartz. The substratesupport may be a platter-like member with low thermal mass, or aring-like member.

Other embodiments described herein provide methods of processing asubstrate by disposing the substrate in a chamber having a transparentfloor, heating the substrate by transmitting radiation from a pluralityof lamps through the transparent floor, depositing a layer on thesubstrate by flowing a precursor gas across the substrate substantiallyparallel to a surface of the substrate, detecting a first temperature ata first zone of the substrate using a first sensor disposed proximatethe transparent floor, detecting a second temperature at a second zoneof the substrate using a second sensor disposed proximate thetransparent floor, adjusting power to a first portion of the pluralityof lamps based on the first temperature, and adjusting power to a secondportion of the plurality of lamps based on the second temperature.Following processing, the substrate may be removed, and a cleaning gashaving chlorine, bromine, or iodine may be provided to the chamber toremove deposits.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic cross-sectional view of a process chamberaccording to one embodiment.

FIG. 2 is a flow diagram summarizing a method according to anotherembodiment.

DETAILED DESCRIPTION

A chamber capable of zoned temperature control of a substrate whileperforming an epitaxy process has a processing vessel with an upperportion, a side portion, and a lower portion all made of a materialhaving the capability to maintain its shape when high vacuum isestablished within the vessel. At least the lower portion is transparentto thermal radiation, and thermal lamps are positioned in a conicallamphead structure coupled to the lower portion of the processing vesselon the outside thereof. Thermal sensors are disposed at variouslocations inside the processing vessel with means for reducing thermalnoise into the sensors and material deposition on the sensors.

FIG. 1 is a schematic cross-sectional view of a process chamber 100according to one embodiment. The process chamber 100 may be used toprocess one or more substrates, including the deposition of a materialon an upper surface of a substrate 108. The process chamber 100generally includes an array of radiant heating lamps 102 for heating,among other components, a back side 104 of a substrate support 107disposed within the process chamber 100. The substrate support 107 maybe a ring-like substrate support as shown, which supports the substratefrom the edge of the substrate, a disk-like or platter-like substratesupport, or a plurality of pins, for example three pins. The substratesupport 107 is located within the process chamber 100 between an upperdome 128 and a lower dome 114. The substrate 108 (not to scale) can bebrought into the process chamber 100 and positioned onto the substratesupport 107 through a loading port 103.

The substrate support 107 is shown in an elevated processing position,but may be vertically traversed by an actuator (not shown) to a loadingposition below the processing position to allow lift pins 105 to contactthe lower dome 114, passing through holes in the substrate support 107,and raise the substrate 108 from the substrate support 107. A robot (notshown) may then enter the process chamber 100 to engage and remove thesubstrate 108 therefrom though the loading port 103. The substratesupport 107 then may be actuated up to the processing position to placethe substrate 108, with its device side 116 facing up, on a front side110 of the substrate support 107.

The substrate support 107, while located in the processing position,divides the internal volume of the process chamber 100 into a processgas region 156 (above the substrate) and a purge gas region 158 (belowthe substrate support 107). The substrate support 107 is rotated duringprocessing by a central shaft 132 to minimize the effect of thermal andprocess gas flow spatial anomalies within the process chamber 100 andthus facilitate uniform processing of the substrate 108. The substratesupport 107 is supported by the central shaft 132, which moves thesubstrate 108 in an up and down direction 134 during loading andunloading, and in some instances, processing of the substrate 108. Thesubstrate support 107 is typically formed from a material having lowthermal mass or low heat capacity, so that energy absorbed and emittedby the substrate support 107 is minimized. The substrate support 107 maybe formed from silicon carbide or graphite coated with silicon carbideto absorb radiant energy from the lamps 102 and conduct the radiantenergy to the substrate 108. The substrate support 107 is shown in FIG.1 as a ring with a central opening to facilitate exposure of thesubstrate to the thermal radiation from the lamps 102. The substratesupport 107 may also be a platter-like member with no central opening.

In general, the upper dome 128 and the lower dome 114 are typicallyformed from an optically transparent material such as quartz. The upperdome 128 and the lower dome 114 are thin to minimize thermal memory,typically having a thickness between about 3 mm and about 10 mm, forexample about 4 mm. The upper dome 128 may be thermally controlled byintroducing a thermal control fluid, such as a cooling gas, through aninlet portal 126 into a thermal control space 136, and withdrawing thethermal control fluid through an exit portal 130. In some embodiments, acooling fluid circulating through the thermal control space 136 mayreduce deposition on an inner surface of the upper dome 128.

One or more lamps, such as an array of lamps 102, can be disposedadjacent to and beneath the lower dome 114 in a specified, optimaldesired manner around the central shaft 132 to heat the substrate 108 asthe process gas passes over, thereby facilitating the deposition of amaterial onto the upper surface of the substrate 108. In variousexamples, the material deposited onto the substrate 108 may be a groupIII, group IV, and/or group V material, or may be a material including agroup III, group IV, and/or group V dopant. For example, the depositedmaterial may include gallium arsenide, gallium nitride, or aluminumgallium nitride.

The lamps 102 may be adapted to heat the substrate 108 to a temperaturewithin a range of about 200 degrees Celsius to about 1200 degreesCelsius, such as about 300 degrees Celsius to about 950 degrees Celsius.The lamps 102 may include bulbs 141 surrounded by an optional reflector143. Each lamp 102 is coupled to a power distribution board (not shown)through which power is supplied to each lamp 102. The lamps 102 arepositioned within a lamphead 145 which may be cooled during or afterprocessing by, for example, a cooling fluid introduced into channels 149located between the lamps 102. The lamphead 145 conductively cools thelower dome 104 due in part to the close proximity of the lamphead 145 tothe lower dome 104. The lamphead 145 may also cool the lamp walls andwalls of the reflectors 143. If desired, the lampheads 145 may or maynot be in contact with the lower dome 114.

A circular shield 167 may be optionally disposed around the substratesupport 107 and coupled to sidewall of the chamber body 101. The shield167 prevents or minimizes leakage of heat/light noise from the lamps 102to the device side 116 of the substrate 108 in addition to providing apre-heat zone for the process gases. The shield 167 may be made from CVDSiC coated sintered graphite, grown SiC, or a similar opaque materialthat is resistant to chemical breakdown by process and cleaning gases.

A reflector 122 may be optionally placed outside the upper dome 128 toreflect infrared light that is radiating off the substrate 108 back ontothe substrate 108. Due to the reflected infrared light, the efficiencyof the heating will be improved by containing heat that could otherwiseescape the process chamber 100. The reflector 122 can be made of a metalsuch as aluminum or stainless steel. The reflector 122 can have machinedchannels 126 to carry a flow of a fluid such as water for cooling thereflector 122. If desired, the efficiency of the reflection can beimproved by coating a reflector area with a highly reflective coatingsuch as with gold.

A plurality of thermal radiation sensors 140, which may be pyrometers,are disposed in the lamphead 145 for measuring thermal emissions of thesubstrate 108. The sensors 140 are typically disposed at differentlocations in the lamphead 145 to facilitate viewing different locationsof the substrate 108 during processing. Sensing thermal radiation fromdifferent locations of the substrate 108 facilitates comparing thethermal energy content, for example the temperature, at differentlocations of the substrate 108 to determine whether temperatureanomalies or non-uniformities are present. Such non-uniformities canresult in non-uniformities in film formation, such as thickness andcomposition. At least two sensors 140 are used, but more than two may beused. Different embodiments may use three, four, five, six, seven, ormore sensors 140.

Each sensor 140 views a zone of the substrate 108 and senses the thermalstate of a zone of the substrate. The zones may be oriented radially insome embodiments. For example, in embodiments where the substrate 108 isrotated, the sensors 140 may view, or define, a central zone in acentral portion of the substrate 108 having a center substantially thesame as the center of the substrate 108, with one or more zonessurrounding the central zone and concentric therewith. It is notrequired that the zones be concentric and radially oriented, however. Insome embodiments, zones may be arranged at different locations of thesubstrate 108 in non-radial fashion.

The sensors 140 are typically disposed between the lamps 102, forexample in the channels 149, and are usually oriented substantiallynormal to the substrate 108. In some embodiments the sensors 140 areoriented normal to the substrate 108, while in other embodiments, thesensors 140 may be oriented in slight departure from normality. Anorientation angled within about 5° of normal is most frequently used.

The sensors 140 may be attuned to the same wavelength or spectrum, or todifferent wavelengths or spectra. For example, substrates used in thechamber 100 may be compositionally homogeneous, or they may have domainsof different compositions. Using sensors 140 attuned to differentwavelengths may allow monitoring of substrate domains having differentcomposition and different emission responses to thermal energy.Typically, the sensors 140 are attuned to infrared wavelengths, forexample about 4 μm.

A top thermal sensor 118 may be disposed in the reflector 122 to monitora thermal state of the upper dome 128, if desired, or to monitor thethermal state of the substrate 108 from a viewpoint opposite that of thesensors 140. Such monitoring may be useful to compare to data receivedfrom the sensors 140, for example to determine whether a fault exists inthe data received from the sensors 140. The top thermal sensor 118 maybe an assembly of sensors in some cases, featuring more than oneindividual sensor. Thus, the chamber 100 may feature one or more sensorsdisposed to receive radiation emitted from a first side of a substrateand one or more sensors disposed to receive radiation from a second sideof the substrate opposite the first side.

A controller 160 receives data from the sensors 140 and separatelyadjusts power delivered to each lamp 102, or individual groups of lampsor lamp zones, based on the data. The controller 160 may include a powersupply 162 that independently powers the various lamps or lamp zones.The controller 160 can be configured with a desired temperature profile,and based on comparing the data received from the sensors 140, thecontroller 160 adjusts power to lamps and/or lamp zones to conform theobserved thermal data to the desired temperature profile. The controller160 may also adjust power to the lamps and/or lamp zones to conform thethermal treatment of one substrate to the thermal treatment of anothersubstrate, in the event chamber performance drifts over time.

FIG. 2 is a flow diagram summarizing a method 200 according to anotherembodiment. At 202, a substrate is positioned on a substrate support ina process chamber. The substrate support is substantially transparent tothermal radiation and has low thermal mass. Thermal lamps are positionedto provide heat to the substrate.

At 204, a process gas is introduced to the process chamber, and pressureof the process chamber is set between about 0.01 Torr and about 10 Torr.The process gas may be any gas from which a layer is to be formed on thesubstrate. The process gas may contain a group IV precursor and/or groupIII and group V precursors, from which a group IV material, such assilicon or germanium, or a group III/V compound material, such asaluminum nitride, may be formed. Mixtures of such precursors may also beused. The process gas is typically flowed with an unreactive diluent orcarrier gas, and is typically provided in laminar or quasi-laminar flowsubstantially parallel to the substrate surface.

At 206, the substrate is heated to a temperature between about 400° C.and about 1,200° C., for example about 600° C. The precursors contactthe heated substrate surface and form a layer on the substrate surface.The substrate may be rotated to improve uniformity of film properties.

At 208, a first temperature of a first zone of the substrate is measuredby a first optical sensor and a second temperature of a second zone ofthe substrate is measured by a second optical sensor. The opticalsensors may be pyrometers sensing intensity of radiation emitted by thesubstrate in the first and second zones. In some embodiments, thesignals received from the optical sensors may be adjusted to compensatefor background radiation emanating from the lamps and reflected from thesubstrate. The substrate reflectivity as a function of temperature,along with the known intensity of light emitted by the lamps, may beused to model the intensity of reflected light, and the modeledintensity used to adjust the signals from the optical sensors to improvethe signal to noise ratio of the sensors.

At 210, power to the lamps is adjusted based on the first temperatureand the second temperature readings to conform the first temperature toa first target temperature and to conform the second temperature to asecond target temperature. The first and second target temperatures maybe the same or different. For example, to compensate for faster filmformation at an edge of the substrate than at the center of thesubstrate, the first temperature may be measured at the center of thesubstrate, the second temperature may be measured at the edge of thesubstrate, and lamp power adjusted to provide a higher substratetemperature at the center than at the edge of the substrate. More thantwo zones may be used to monitor temperatures at more than two locationson the substrate to increase the specificity of local temperaturecontrol, if desired.

At 212, processing is stopped and the substrate is removed from theprocess chamber. At 214, a cleaning gas is provided to the chamber toremove deposits from chamber surfaces. Removing the deposits correctsreduction in transmissivity of chamber components to lamp radiation andto substrate emissions, maintaining repeatability of film propertiesfrom substrate to substrate. The cleaning gas is typically a gascontaining chlorine, bromine, or iodine. Gases such as Cl₂, Br₂, I₂,HCl, HBr, and Hl are often used. When elemental halogens are used,temperature of the chamber may be held approximately constant, orincreased slightly, to clean the chamber. When hydrogen halides areused, temperature of the chamber is typically increased to compensatefor reduced concentration of halogen cleaning agents. Temperature of thechamber during cleaning with hydrogen halides may be increased tobetween about 800° C. and about 1,200° C., for example about 900° C.After cleaning from 30 seconds to 10 minutes, depending on the desiredcleaning result, another substrate may be processed.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

The invention claimed is:
 1. A substrate processing apparatus,comprising: a vacuum chamber comprising a transparent dome and atransparent floor, wherein both the transparent dome and the transparentfloor are quartz; a substrate support disposed inside the vacuumchamber, wherein the substrate support is a platter-like member with lowthermal mass; a plurality of thermal lamps arranged in a lamphead andpositioned proximate the transparent floor of the vacuum chamber; aplurality of thermal sensors disposed within the lamphead and orientedto receive thermal radiation from an area proximate the substratesupport, wherein the thermal sensors receive thermal radiation throughthe transparent floor, and wherein the thermal sensors receive thermalradiation emitted by the substrate and transmitted by the substratesupport; a plurality of power supplies coupled to the thermal lamps inrelation to the position of the thermal sensors; a controller thatadjusts the power supplies based on input from the thermal sensors; anda reflector disposed proximate the transparent dome, the reflector andthe transparent dome together defining a thermal control space.
 2. Thesubstrate processing apparatus of claim 1, further comprising an inletfor a thermal control fluid disposed through the reflector in fluidcommunication with the thermal control space, and an outlet for thethermal control fluid disposed through the reflector and in fluidcommunication with the thermal control space.
 3. The substrateprocessing apparatus of claim 1, further comprising a thermal sensordisposed proximate the transparent dome.
 4. The substrate processingapparatus of claim 3, wherein the thermal sensor is disposed in thereflector.
 5. A substrate processing apparatus, comprising: a vacuumchamber comprising a transparent dome and a transparent floor; asubstrate support disposed inside the vacuum chamber, wherein thesubstrate support is a platter-like member with low thermal mass; aplurality of thermal lamps arranged in a lamphead and positionedproximate the transparent floor of the vacuum chamber; a plurality ofthermal sensors disposed within the lamphead and oriented to receivethermal radiation from an area proximate the substrate support, whereinthe thermal sensors receive thermal radiation through the transparentfloor, and wherein the thermal sensors receive thermal radiation emittedby the substrate and transmitted by the substrate support; a pluralityof power supplies coupled to the thermal lamps in relation to theposition of the thermal sensors; a controller that adjusts the powersupplies based on input from the thermal sensors; a reflector disposedproximate the transparent dome, the reflector and the transparent dometogether defining a thermal control space; and an inlet for a thermalcontrol fluid disposed through the reflector in fluid communication withthe thermal control space, and an outlet for the thermal control fluiddisposed through the reflector and in fluid communication with thethermal control space.
 6. The substrate processing apparatus of claim 5,further comprising a thermal sensor disposed proximate the transparentdome.
 7. The substrate processing apparatus of claim 6, wherein thethermal sensor is disposed in the reflector.
 8. A substrate processingapparatus, comprising: a vacuum chamber comprising a transparent domeand a transparent floor; a substrate support disposed inside the vacuumchamber, wherein the substrate support is a platter-like member with lowthermal mass; a plurality of thermal lamps arranged in a lamphead andpositioned proximate the transparent floor of the vacuum chamber; aplurality of first thermal sensors disposed within the lamphead andoriented to receive thermal radiation from an area proximate thesubstrate support, wherein the first thermal sensors receive thermalradiation through the transparent floor, and wherein the first thermalsensors receive thermal radiation emitted by the substrate andtransmitted by the substrate support; a plurality of power suppliescoupled to the thermal lamps in relation to the position of the firstthermal sensors; a controller that adjusts the power supplies based oninput from the first thermal sensors; a reflector disposed proximate thetransparent dome, the reflector and the transparent dome togetherdefining a thermal control space; and a second thermal sensor disposedproximate the transparent dome.
 9. The substrate processing apparatus ofclaim 8, wherein the second thermal sensor is disposed in the reflector.